Rationale: To develop a more effective treatment for nicotine addiction is a public health priority. In order to do so a better understanding is needed of the mechanisms 1) underlying nicotine addiction and 2) the way treatments alter the way nicotine transiently and permanently alters multiple cognitive and executive functions. Most effects of nicotine on the Central Nervous System (CNS) are directly mediated by nicotine molecules. Treatment with 3'aminomethylnicotine P. aeruginosa r-Exoprotein A Conjugate Vaccine (NicVAX™) stimulates the production of nicotine specific antibodies. These antibodies bind the small nicotine molecules, preventing them to cross the Blood Brain Barrier (BBB) and thus preventing CNS stimulation. A nicotine challenge given after vaccination will show no or diminished direct effects of nicotine on CNS stimulation. The blocking effects of the nicotine specific antibodies will be evaluated on several cognitive tasks and on reactivity to smoking-related cues.